The present invention relates to a method for manufacturing semiconductor devices and, more particularly, to a plasma processing method in which plasma etching is conducted.
In recent years, along with higher integration of semiconductor devices, shallow-trench isolation (hereinafter abbreviated STI) techniques have been used as a device isolation method.
In an STI technique, a silicon substrate is first plasma-etched, for example, using a silicon nitride film as a mask to form trenches for device isolation. The formed trenches are then filled with a silicon oxide film and unwanted portions of the silicon oxide film are removed by chemical mechanical polishing (CMP) so that STI regions are formed.
JP-A-2003-007679 discloses a method for performing etching by plasma etching using gases including at least Cl2 and HBr as a method for forming trenches for device isolation.
Furthermore, along with higher integration of semiconductor devices of recent years, higher miniaturization has been required; in STI techniques for the next-generation semiconductor devices, trenches having a depth of about 300 nm are required to be formed using a mask having an opening width of 20 nm or less.